The present invention relates generally to interface devices for allowing humans to interface with computer systems, and more particularly to computer interface devices that allow the user to provide input to computer systems and allow computer systems to provide force feedback to the user.
Users interact with computer systems for a variety of reasons. A computer system typically displays a visual environment to a user on a display output device. Using an interface device, a user can interact with the displayed environment to perform functions and tasks on the computer, such as playing a game, experiencing a simulation or virtual reality environment, using a computer aided design system, operating a graphical user interface (GUI), or otherwise influencing events or images depicted on the screen. Common human-computer interface devices used for such interaction include a joystick, mouse, trackball, stylus, tablet, pressure-sensitive ball, or the like, that is connected to the computer system controlling the displayed environment. Typically, the computer updates the environment in response to the user's manipulation of a user-manipulatable physical object such as a joystick handle or mouse, and provides visual and audio feedback to the user utilizing the display screen and audio speakers. The computer senses the user's manipulation of the user object through sensors provided on the interface device that send locative signals to the computer. For example, the computer displays a cursor, controlled vehicle, or other graphical object in a graphical environment, where the location or motion of the graphical object is responsive to the to the motion of the user object. The user can thus control the graphical object by moving the user object.
In some interface devices, tactile and/or haptic feedback is also provided to the user, more generally known as "force feedback." These types of interface devices can provide physical sensations which are felt by the user manipulating a user manipulable object of the interface device. For example, the Force-FX joystick controller from CH Products, Inc. and Immersion Corporation may be connected to a computer and provides forces to a user of the controller. Other systems might use a force feedback mouse controller. One or more motors or other actuators are coupled to the joystick or other user object and are connected to the controlling computer system. The computer system controls forces on the joystick in conjunction and coordinated with displayed events and interactions by sending control signals or commands to the actuators. The computer system can thus convey physical force sensations to the user in conjunction with other supplied feedback as the user is grasping or contacting the joystick or other object of the interface device. For example, when the user moves the manipulatable object and causes a displayed cursor to interact with a different displayed graphical object, the computer can issue a command that causes the actuator to output a force on the user object, conveying a feel sensation to the user.
A common use for force feedback interface devices such as joysticks is in video game applications, either in first person or third person perspectives. In first person virtual reality games, the player may fly a simulated aircraft or spaceship, move a warrior in a fighting game, etc. In third person games, the player may control a vehicle, person, or object as if viewing the object from an exterior view. Sensors on the joystick allow the user to influence motion of the airplane or other entity, while actuators on the joystick allow the user to feel realistic force sensations. For example, an aircraft is flown into a simulated storm, where the host computer issues a force command that causes the actuators to create a feel of turbulence. This turbulence shakes the joystick in a convincing manner coordinated with the simulated storm. In other applications, a user-controlled cursor in a graphical environment such as a graphical user interface is well suited for use with force feedback.
A current problem with the prior art force feedback interfaces is that force sensations output by the devices are often predefined, "canned" sensations that are simply output by the interface device when instructed by the host computer. For example, a jolt force may be output by the actuators of the force feedback device in response to an event occurring in a game, such as a collision of a controlled vehicle with an obstacle such as a wall. The prior art force feedback devices simply output a jolt force in a specified direction having a predetermined duration and magnitude. While effective to relay the collision experience to some extent, this jolt may also be unsatisfying for the user, since the user has no way to affect the jolt based on the user's input during the jolt's duration. For example, the user cannot, in anticipation of the collision, cushion the jolt caused by the impact by moving the joystick in the same direction as the jolt or moving the joystick in other ways.
Other force sensations provided by the prior art force feedback devices may be dependent on user input, but only in limited ways. For example, a force feedback interface device may output a damping force in conjunction with a user's "character" traveling through an expanse of liquid, such as swamp muck. The damping force can be modelled as a damping constant multiplied by the velocity of the joystick. Thus, the user feels a different damping force magnitude depending on how fast the joystick is moved. However, this is a crude, simplistic effect, for it fails to take into account undulations or waves in the swamp muck which the user may feel and which may cause the damping force to vary in magnitude and direction. In addition, the user is unable to provide input or skill in changing the affects of the damping to achieve a desired game effect. For example, the player cannot move through the swamp muck in a dexterous manner that absorbs undulations in the liquid to thereby gain greater speed in traveling through the muck, since the simple damping model will not allow this type of interaction.
Furthermore, a programmer of force feedback applications needs a protocol and set of commands which will easily allow the implementation of more realistic and interactive force sensations. Application program developers are concerned with providing high quality programs that include immersive force feedback, but they do not have the time and expertise to program force control routines from scratch.
Another problem with the prior art development of force feedback sensations in software is that the programmer of force feedback applications does not have an intuitive sense as to how forces will feel when adjusted in certain ways, and thus must go to great effort to develop characteristics of forces that are desired for a specific application. For example, a programmer may wish to create a specific spring and damping force sensation between two graphical objects, where the force sensation has a particular stiffness, play, offset, etc. In current force feedback systems, the programmer must determine the parameters and characteristics of the desired force by a brute force method, by simply setting parameters, testing the force, and adjusting the parameters in an iterative fashion. This method is cumbersome because it is often not intuitive how a parameter will affect the feel of a force as it is actually output on the user object; the programmer often may not even be close to the desired force sensation with initial parameter settings. Thus, a tool is needed for assisting the programmer or developer in intuitively and easily setting force feedback characteristics to provide a desired force sensation.